Cross-Scale Prediction Model of Oxygen Diffusion in Concrete Under Dry Conditions

The rate of oxygen diffusion directly affects the distribution of oxygen concentration within concrete, which in turn influences the corrosion performance of reinforcing steel within the concrete. However, research on cross-scale prediction models for oxygen diffusion in dry concrete is still lacking. In this study, the complex pore structure of concrete is simplified into a sponge model, and three types of diffusion are quantitatively characterized based on the pore size distribution density function. The influence of porosity, water–cement ratio, hydration degree, gel–space ratio and pore tortuosity on the oxygen diffusion coefficient is considered, and a cross-scale prediction model for oxygen diffusion in dry concrete is established. Secondly, an oxygen diffusion coefficient determination device developed independently is used to measure the oxygen diffusion coefficient of concrete specimens under dry conditions. The results show that the experimental values agree well with the calculated values, and the model is compared with other models proposed by scholars, verifying its superiority and accuracy. Finally, a parameter sensitivity analysis is conducted on five microscale parameters and their influence on the behavior of oxygen transmission into concrete is discussed. The establishment of the cross-scale prediction model for oxygen diffusion in dry concrete will first provide a positive role in the theoretical research on reinforcement expansion and cracking, and secondly, it will be able to better explain the mechanism of oxygen diffusion in concrete.